It's always scary making a film as I never set anything up or ask anyone to do anything, so I worry that we'll find a story. I have to trust that a film will come out of the journey we embark on. I have many, many sleepless nights.

Personally, I don't like watching films about victims - people where you're meant to think, 'Oh, this is terrible,' and you go home feeling really depressed.

It makes it very easy. I have a beginning, middle, and end, and I don't film for long - about 20 hours usually for a two-hour film - so it's easily watchable in a week for me and the editor. Once I know who the characters are, I only film those characters, unless somebody else forces their way into the film by a scene happening to them or we meet them by chance.

I know that sounds contradictory - you're going on a journey, but once you know who your characters are, you become more disciplined and you film less and less.

There's no point in making something if you're not falling in love with the people you're filming and you want them to really enjoy you being around. It would be weird if, when you're making a film, you don't think it's going to be the best ever or the worst ever - I guess it goes from one feeling to another.

I watch mainly fiction. The films I like watching are films where you see people change, like with Boyhood. You see a moment in someone's life where it's a breakthrough. For me, the breakthrough in Boyhood is that amazing moment right at the end when he finds somebody he can feel relaxed with, and who will maybe be a friend for the rest of his life. I like that it doesn't end in a love affair or marriage. It just ends in, "Wow, I found people I can relate to for the first people in my life. These people accept me, I like them."

I don't have any advice at all. I think we all make the films that reflect the kind of people we are; we all make such different films. There's not just one way of doing it.